Oscillator circuit



1933- E. R. HENTSCHEL OSCILLATOR CIRCUIT Filed May 23, 19150 2 Sheets-Sheet 1 IN VEN TOR. $1M! 61- M0606,

BY wmqwm ATTORNEY Patented Nov. 7, 1933 9 UNITED STATES PATENT OFFICE Olson,

administrator of said Ernest R.

Hentschel, deceased, assignor to Wired Radio, Inc., New York, N. Y., acorporation of Delaware Application May 23, 1930. Serial No. 455,133

8 Claims.

My invention relates broadly to oscillator circuits and more particularly to a combination frequency controlled and self-oscillating circuit.

One of the objects of my invention is to provide an arrangement of oscillating circuit which can be adjusted so that the circuit will oscillate at exactly the same frequency either in the frequency controlled condition or in the self-oscil-. lating condition.

Another object of my invention is to provide an arrangement of oscillating circuit having means for automatically changing the mode of oscillation thereof in accordance withthe insertion or removal of a frequency controlling ele- '15.ment with respect to the oscillating circuit.

A further object of my invention is to .provide an arrangement of oscillating circuit having means for sustaining self-oscillations or oscillations controlled by a frequency fixing element with means for automatically changing the characteristics of the oscillatingcircuit in accordance with the insertion or removal of the frequency element with respect to the oscillating, circuit.

Other and further objects of my invention will be understood from the specification hereinafter following by reference to the accompanying drawings, in which: V

Figure l is a cross-sectional view partially in side elevation through a mounting for .the frequency fixing device and automatic circuit controlling apparatus; Fig. 2 is a view of the apparatus illustrated in Fig. l withthe frequency fixing device removed therefrom and showing the position of the automatic circuit controlling apparatus when the frequency fixing device is so removed; Fig. 3 is an end view of the apparatus illustrated in Fig. 1 looking in the direction of arrow 3 in Fig. 1; Fig. 4 is a crosssectional view through the apparatus on line 4-4 of Fig. 2; Fig. 5 is a circuit arrangement showing the cooperative relation of the frequency fixing device and parts of an oscillating system which is capable of change from an oscillating condition to a non-oscillating condition; and Fig. 6 is a modified circuit arrangement embodying the principles of my invention.

My invention is directed to an oscillating system having means for the automatic adjustment of the system for oscillation at exactly the same frequency in either a self-oscillating condition or in a frequency controlled condition. For the purpose of controlling the'frequency of oscillations generated in the oscillating circuit, I utilize a piezo-electric crystal device ground to a predetermined frequency. The piezo-electric crystal device is mounted in a suitable container and is capable of being inserted in or removed from the oscillating circuit. In lieu of a piezoelectriccrystal element, I may employ a magnetostriction device or other form of frequency fixing apparatus. In an oscillating system employing an electron tube, a tank circuit is provided containing inductance and capacity. For the. operation of the oscillating system either under a frequency controlled condition or a selfoscillating condition, the natural frequency of the tank circuit must be higher for the frequency controlled oscillations than for self-oscillations. Therefore, to secure operation at the same frequency provision must be made for changing the tuning of the tank circuit depending upon whether the frequency controlling element is connected in the oscillating system or removed therefrom. I provide a mounting for apiezoelectric crystal holder having means for automatically changing the capacity of an electrical condenser in accordance with the insertion of the piezo-electric crystal holder into the mounting or the removal of the holder therefrom. The electrical capacity of the condenser forming part of the mounting apparatus is larger when the piezo-electric crystal holder is removed than it is when the piezo-electric crystal holder is inserted in the mounting appparatus.

Referring to the drawings in detail, reference character 1 designates a socket arranged to receive the crystal holder 10. The mounting for the socket 1 consists of a base 2 of insulated ma- I terial to which there is secured a spring member 6to which connection may be made through binding post 8. Binding post 7 is mounted on the base 2 in alignment with a contact 9, which is carried by the spring strip 6. The lower end of the crystal holder 10, which is closed by the contact plate 33a, establishes connection with the strip 6 which is shaped to establish resilient contact with the crystal holder and govern the position of strip 6. The crystal holder has been broken away in Fig. l to show the piezo-electric crystal element 33 therein resting on lower contact plate 33a with the upper surface of the crystal element 33 electrically connected to upper contact plate 33b which is connected interiorly of the. crystal holder to the upper portion 12 of the holder, connection being made to pins 11 which engage bayonet slots 13 with socket 1 which forms one terminal for the frequency control device. The other terminal for the frequen- Q cy control device is formed by lower contact plate 33a which connects with strip 6. The strip 6 has an extended portion which is aligned with a fixed plate member supported beneath the mounting base 2, which plate covered by insulation sheet 4 preventing contact between the extension of strip 6 and the plate Binding post 3a is provided on plate for establishing connection with the fixed plate 3 and adjusting screw 39 extends through base 2 and through insulated bushings 41 for preventing electrical contact between adjusting screw 39 and fixed plate 3. The adjusting screw 39 forms a limiting abutment against the movement of the strip 6 for controlling the maximum capacity of the condenser formed by the alignment of the extended endless strip 6 with respect to the fixed plate 3. That is to say, if adjusting screw 39 is withdrawn from base 2 the maximum capacity of the condenser formed between strip 6 and plate 3 is increased by the reduction in the spacial relation of plate 3 and strip 6. On the other hand, if screw 39 is ad vanced through the base 3, the value of the capacity obtainable between strip 6 and plate 3 is reduced. The minimum capacity of the condenser formed between stri p 6 and plate 3 is limited by the adjustment of screw mounted in a portion of the mounting base 2 as shown. It will be clear from a consideration of Figs. 1-4 that the insertion of a piezo-electric crystal holder into the socket operates to open the circuit between binding post I and contact 9 and to decrease the capacity formed by the extension of strip 6 and capacity of the plate 3.

In the circuit diagram of Fig. 5 an electron tube has been indicated at including a cathode 15a, a grid 15b and a plate 150. An inductance 19 is provided in the plate circuit connected in series with by-pass condenser 20 and in series with grid inductance 26 which electrically connects through the frequency control device with the grid condenser 27 to the grid electrode 151). A grid leak 29 connects between grid electrode 151) and cathode 15a. The frequency control device ineluding piezo-electric crystal 33 is shown removably connected in the input circuit of the electron tube system.

In order to clearly represent the removability of the piezo-electric crystal device I have indicated connections between the electrodes 33a and 33b through arrow heads with the terminals which connect to the input circuit of the oscillator. A condenser 32 is permanently connected inv series with the removable piezo-electric crystal device for the regulation of regeneration. The switch represented at 30 corresponds to the contact 9 and binding post 7 illustrated in Figs. 1 and 2. The condenser 31 corresponds to the condenser formed by the extension of the strip 6 and the fixed plate 3. In order that it will be clearly understood that the operation of switch 30 directly depends upon the insertion of the crystal device in the socket and that the capacity of condenser 31 is directly proportional to the movement of switch 30 in accordance with the insertion or removal of the piezo-electric crystal holder, I have shown the coordinated operation of these several parts by arrow 42. A blocking condenser 16 is connected in series with the variable capacity 31 and is connected to the output circuit of the electron tube 15. A direct current ammeter 21 is connected in the output circuit in series with the plate inductance 19 and in series with the high potential source 23 which connects to one side of the cathode 15a through the 5 which iscathode heating circuit which contains battery 24 and adjusting rheostat 25. When the circuit is used as a self oscillating one, holder 10 removed, switch 30 is closed and the capacity of condenser 31 is decreased. Now if the circuit had been so adjusted that the self oscillating frcquency was exactly that of the crystal, and if condenser 31 (3, 4, 6 of Fig. 1) were so constructed that its change in capacity were suificient, the crystal oscillations would be of exactly the same frequency as that of the self oscillating condition. If the change in capacity is correct, the circuit constants are right for best operation of the crystal. For the same frequency in both conditions, the natural frequency of the tuned circuit must be higher for crystal oscillations than for selfoscillations. This is the reason for using condenser 31 to automatically change th s natural frequency.

As illustrated in Fig. 6, my invention is applicable to an oscillation circuit connected to an antenna ground system 43-44 of a radio receiver. In this arrangement the condenser 31 is connected in shunt with the input circuit or" the electron tube 15. Removal of the crystal holder increases the capacity across the input circuit of the tube system while insertion of the crystal holder decreases the capacity across the input system.

In order to set tuning condenser 18 at the right value in the self-oscillating condition to match a certain crystal frequency another oscillating circuit must be used in conjunction with the oscillating circuit which has been illustrated. In initially calibrating the apparatus the piezo-electrio crystal is inserted in the circuit for establishing oscillations and the other oscillating circuit is tuned to resonance therewith. The piezoelectric crystal is then removed and the other oscillating circuit tuned to resonance with the circuit illustrated. By properly compensating IOl the diiference in frequency the two frequencies may be matched to within something like two or three cycles so that the circuit oscillates at the same frequency with or without the frequency control device connected in the circuit.

In the circuit arrangement shown in Fig. 6 the number of leads covering high radio frequency potentials is reduced. The effect on the tuned circuit is therefore less as this arrangement places the condenser 31 across the input inductance 26 only instead of across the input and output inductances 26 and 19 as in the arrange- 151 8111; in Fig. 5.

My invention has proven highly eflicient in its operation as it provides a very flexible circuit which can be used either with or without a piezoelectric crystal and it combines an oscillator and an accurate frequency meter into one circuit thus eliminating the need of a separate frequency meter or crystal oscillator. With a few crystals the entire range of the circuit can be accurately calibrated so that a transmitter using this circuit as a master oscillator may be ac curately set on many frequencies. By making the capacity of condenser 32 small it is possible to use a tube of high power, thus permitting the generation of a great deal of power in the self oscillating condition while only a small amount will be generated in the crystal oscillating condition, thus protecting the crystal.

My circuit can be used as a heterodyne re ceiver, by coupling to an antenna ground circuit 4344 through dotted condenser 45 and inserting telephones or an audio-frequency transformer at 22. When used as an oscillator sup- 150 plying energy for either reception or transmission, coupling may be obtained through another coil coupled to the coil 19 or coil 26 or both, or through a condenser in the usual manner.

While I have described my invention in certain preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. An oscillator circuit including an electron tube having grid, filament, and plate electrodes, a tank circuit connected with said electrodes, means for adjusting the frequency of said tank circuit, a frequency determining element connectible with said electrodes, and means operative simultaneously with the connection or disconnection of said frequency determining element with said electrodes for shifting the frequency of said tank circuit.

2. An oscillator circuit including an electron tube having grid, filament, and plate electrodes, a tank circuit connected to said electrodes, means for adjusting the frequency of said tank circuit, a frequency determining element connectible with said oscillator circuit, and means automatically controllable by the connection or disconnection of said frequency determining element with said oscillator circuit for changing the frequency of said tank circuit.

3. An oscillator system comprising an electron tube having grid, filament, and plate electrodes, a tank circuit connected with said electrodes, means for adjusting the frequency of said tank circuit, a frequency determining element, means for connecting or disconnecting said frequency determining element with said electrodes, and means connected in circuit to said tank circuit and operative automatically upon the connection or disconnection of said frequency determining element with said electrodes for changing the frequency characteristics of said tank circuit.

4. An oscillator system including an electron tube, grid, cathode and plate electrodes therein, a tank circuit connected with said oscillator system, means for adjusting the frequency of said I tank circuit, a frequency determining element connectible with said electrodes, a variable condenser connected with said oscillator system, and

'an angularly movable member extending from said variable condenser and arranged to be shifted in position by the insertion or removal of said frequency determining element into or out of connection with said electrodes, for changing the effective capacity of said condenser with respect to said tank circuit.

5. An oscillator system comprising an electron tube having a plurality of electrodes therein, input and output circuits interconnecting said electrodes, tuning means in one of said circuits, a frequency determining elementv connectible in said input circuit, and a variable impedance element connected with said tuning means and changeable in accordance with the connection or disconnection of said frequency determining element from said input circuit.

6. An oscillator circuit comprising an electron tube including a multiplicity of electrodes, input and output circuits interconnecting said electrodes, tuning means in said output circuit, frequency determining means connectible in said input circuit, and a variable condenser having a fixed plate and a movable plate, said movable plate being arranged to be shifted with respect to said fixed plate by the insertion or removal of said frequency determining means into or out of said input circuit, whereby the capacity of said output circuit is increased when said frequency determining means is inserted in said input cir- 1 5 cuit and is reduced when said frequency determining means is removed from said input circuit.

7. An oscillator system including an electron tube having input and output circuits coupled to sustain oscillations under conditions of self-oscilla-tion or under conditions of controlled oscillations, a frequency determining element connectible with said circuits, and means for automatically changing the tuning of said circuits in accordance with the connection or disconnection 5 of said frequency determining element with respect thereto.

8. A high frequency oscillator comprising an electron tube having a multiplicity of electrodes therein, input and output circuits interconnect- 1 ing said electrodes, a frequency determining element connectible with said circuits, and a variable condenser controllable by the connection or disconnection of said frequency determining element with respect to said circuits for controlling the tuning adjustment of said circuits.

ERNEST R. HENTSCHEL. 

